New coordinate system for the universe

Astronomers adopt new frame of reference for directional data in space

A new reference system will in future make position information more accurate in space © NASA, ESA, and Y.-H. Chu (Academia Sinica, Taipei)
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Celestial Fixed Points: Astronomers have agreed on a new, more accurate reference system for position information in space. This is based on the measurement of more than 4, 000 extragalactic radio sources, which are regarded as fixed points in the reference frame. From January 2019, the sky grid adopted by the International Astronomical Union will apply. By this direction data for spacecraft, but also astronomical observations can be located in the future more precisely.

When spacecraft fly to other planets or astronomers map the movement of stars, they need a reference system - celestial coordinates and fixed points to which they can fix course or position. Because the stars of our Milky Way move over time, astronomers use a reference system based on extragalactic radio sources such as quasars.

"These are supermassive black holes at the center of foreign galaxies, some of which are billions of light years away from us, " explains Johannes Böhm of the Vienna University of Technology. Because of these enormous distances, the position of these quasars hardly changes in the sky. This makes them suitable as reference points for the celestial coordinate system, the so-called International Celestial Reference Frame (ICRF).

More data, greater precision

However, the 2010 reference frame, which has been in place so far, is outdated in terms of precision and number of fixed points, as the International Astronomical Union (IAU) explains: "Since its inception, Very Long Baseline Array (VLBI) observing programs have increased the volume of astrometric and geodetic data almost doubled. "More powerful instruments have also significantly improved the accuracy of celestial position determination.

Therefore, an IAU working group has used this new data in recent years to develop a new frame of reference - a laborious workload with enormous computing power. For this purpose, the observation data of different radio telescopes must be compared with each other in such a way that the noise is minimized and the actual distance and position can be determined as precisely as possible. display

Astronomers at the vote during the General Assembly of the IAU in Vienna. IAU / M. Zamani

4, 000 quasars as measuring points

Now the astronomers have completed the new reference system ICFR3. It is based on the position data of more than 4, 000 extragalactic radio sources and has an accuracy of about 30 micro-arc seconds. This is about the diameter of a tennis ball on the moon, seen from the earth.

On August 30, 2018, the general assembly of the IAU in Vienna decided to officially use this new high-precision radio source card as an international reference system as of 1 January 2019. "It represents significant improvements in the characterization of radio sources, the precision of their positions and the total number of sources, " says the IAU Decision.

For example, the new reference system will be used in the future to indicate the position of spacecraft, planets or stars. However, this celestial map is also important for the observation of the earth, for example when examining the precession of the axis of rotation or the wandering of the poles.

(IAU, Vienna University of Technology, 03.09.2018 - NPO)